Silver alloy



Patented Nov. 12, 1940 PATENT OFFICE SILVER ALLOY Franz R. Hensel,Kenneth L. Emmert, and James W. Wisgs, Indianapolis, Ind., assignors toP. R. Mallory & 00., Inc., Indianapolis, -Ind., a. corporation ofDelaware No Drawing. Application March 21, 1940,

Serial No. 325,188

4 Claims.

This invention relates to a silver alloy suitable for use in place ofpure silver and for uses to which previously known silver alloys havebeen employed, of which may be mentioned particularly, uses of thealloys of the present invention in connection with electrical contacts,silverware, .jewelry and dental alloys.

It is an object of the present invention to provide an alloy which hasimproved electrical properties such as contact resistance.

It is a further object of the present invention to provide an alloywhich shows improved fluidity in the molten state and lends itself tocasting.

It is a. still further object ofthe present invention to produce analloy which has improved tarnish resisting characteristics.

Another object of the present invention is to produce a new alloy whichhas superior electrical characteristics when used as an electricalmake-and-break contact such as low material transfer and freedom fromwelding or sticking. Other objects of the invention will be apparentfrom the following description taken in connection with the appendedclaims. The present invention comprises the combination of elements,methods of manufacture and the product thereof brought out andexemplifi'ed in the disclosure hereinafter set forth, the scope of theinvention being indicated in the appended claims. While a preferredembodiment of the invention is described herein, it is contemplated thatconsiderable variation may be made in the method of procedure alnd thecombination of elements Lrithout departing from the spirit of the inven-The present invention contemplates the addition to silver of magnesiumand lithium. It is contemplated that alloys may be produced according tothe invention, having the ingredients combined in the following range ofproportions:

' Per cent Lii-himn .002 to 3 Magnes .05 to 15 Balance substantially allsilver We have also found that the addition of the following elementsmay improve the characteristics ofthe present alloys covered by thepresent invention:

Per cent Tin up to 11 Manganes up to 20 Nickel up to 10 Phosphorus up to8 Silicon up to 2 It is also possible to substitute copper for asubstantial part of the silver.

A number of preferredcompositions are given below.

Percent a. Magnesium 3.25 Lithium .01 Silver- Balance b. Magnes 2Lithium ,05

' Silver I Balance 3, Magnesium I 5 Lithium .02 Silver Balance 01.Magnesi 3 Lith m .014 Copper 4 10 Silver Balance e. Magnes 3. Lithium,02 Copper 22 Silver Balance In addition to the baser elements,materials from the palladium, platinum or gold group may also be presentup to 10% each.

The alloys of the present invention are preferably prepared by meltingthe in redients together in the correct proportions. The lithium ispreferably added the form of a silver-lithium master alloy, conapproximately 15% of lithium. This master alloy has a very low meltingpoint which is in the neighborhood of 410-450 C. and therefore will soreadily into solution when added to the silver or silvercopper melt.

The efiect of lithium is to completely deoxidize the silver melt andtofree same from other impurities which are harmful. Part of the lithiumwill be eliminated together with these impurities and the remaining meltwill befree from inclusions and oxides. The pre ce of lithium alsoprevents the further oxid tion of the melt during the heating periods towhich the melt may be subjected and the material retains a very highfluidity during pouring, resulting in clean castings. The alloy also hasimproved workability. If lithium is used on proportions such ascontemplated it was found that alloys of silver with magnesium will showgreatly improved electrical characteristics. Contact alloys of this typehave very improved characteristics as far as material transfer andcontact resistance are concerned.

The metal surface is kept clean during operation.

Since lithium decreases the melting point of silver very materially andsince an eutectic is formed at 2.7% lithium, having a melting point of610 C. care must be exercised when these materials are processed atelevated temperatures and if they contain higher percentages of lithium.

While the present invention, as to its objects and advantages, has beendescribed herein as carried out in specific embodiments thereof, it isnot desired to be limited thereby but it is intended to cover theinvention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. An alloy containing .002 to 3% lithium, .05 to 15% magnesium and thebalance substantially all silver.

2. An alloy composed of .002 to 1% lithium, .05

to 4% magnesium and the balance silver.

3. An alloy composed of .002 to .05 lithium, 2 to 4% magnesium and thebalance silver.

4. A silver-magnesium-lithium alloy having better casting and workingproperties, cleaner surface and greater freedom from inclusions andoxides than a silver-magnesium alloy of similar composition, said alloyconsisting of .05 to 15% magnesium, .002 to 3% lithium and the balancesubstantially all silver.

